In the garment manufacturing industry, the production of clothing is accomplished by cutting large, rectangular pieces of material from 100-150 yard rolls, placing stacks of the rectangular pieces of material on a market table for cutting, and positioning a pattern for cutting this material on top of the stack. Cutting of the material is performed either by handknife or by an automatic cloth cutter such as a laser cutter. A computer optimizes the placement of the patterns on the cloth to maximize usage of material. After cutting, the material from which clothing is to be manufactured must be bundled and carried to further processing stations where the material is folded, sewn, or subjected to further processing operations.
One particular type of folded ply encountered in the manufacture of men's dress shirts is the V-top pocket. Many currently fashionable men's dress shirts typically include a breast or pen pocket which has a V-shaped seam on the lower edge and a corresponding V-shaped upper portion or region at the upper part of the pocket, the result of folding a section of the ply under the ply and sewing the folded edge to the ply with a V-shaped stitch. The edges of the V-shaped upper portion are often folded under the seam, to present a smooth, nonfraying boundary when the pocket is sewn to the shirt.
Most if not all V-top pocket are sewn by hand, because of the tedious nature of folding the edge of the ply under the ply before sewing the upper portion to form the V-shaped upper region. Prior to the present invention, it was not thought possible to automate the manufacture of V-top pockets to include the steps of folding the edges under, folding the V-top, sewing the top, and stacking.
A particular difficulty encountered in the manufacture of V-top pockets is the slight folding or undertuck of the edge of the material into the seam. This slight fold or tuck is between 1/4" and 3/8", with a stitch margin of 1/32" to 1/16". The fold or tuck is difficult to make with machinery because of the pliability of the cloth material. Another problem is the formation of the folded upper portion of the pocket, while holding the folded edge in place. Use of an apparatus which transfers the ply with a folded edge to another workstation for forming the fold risks loss of the edge fold unless the folded edge is clamped in place during movement between workstations. Yet another difficulty is the sewing of the V-shaped stitch or seam, while holding the edge fold and the upper portion fold in place.
One approach to forming the tucked edge in a straight hem pocket is shown in U.S. Pat. No. 3,898,941 to Crawford et al. In this patent, the upper portion fold and edge tuck are formed by moving the ply of material along a path on an endless belt, and guiding the edges with folding plates into folded and tucked positions as the ply is moved along the path. While this method works most of the time, occasionally the edge will get double folded or the entire ply will be displaced from the endless belt, since the ply is not positively held during the folding and tucking operation. Moreover, this apparatus can only make a straight hem, and because of its construction cannot form or sew a "V" or other contoured seam.
After a single pocket is folded and sewn, there still remains the problem of stacking the folded pockets so that they may be bundled for transfer to another processing station, such as sewing to the shirt plackets. Since folded plies such as the V-top pocket are thicker at one end than the other due to the fold, it has proven difficult to automatically stack the material due to the tendency of the stack to grow higher toward the end with the fold than at the opposite end. This unevenness in stack height at opposite ends of the stack presents a problem in presenting a stacking surface for pockets presented for stacking and bundling.
Some prior art stacking devices suffer from skewed, uneven stacks due to dropping of a ply onto the stack. This generally results from releasing the article to be stacked to fall onto the stack without positive guidance. Since pliable cloth pockets are susceptible to air currents and unevenness in the stacking surface, releasing a pocket to fall on to the top of a stack often results in skewed or uncentered stacking. This slows down subsequent operations since an operator or subsequent processing machine cannot be certain of picking up an edge of a pocket at the same place in the stack every time.
One approach to the problem of stacking is shown in U.S. Pat. No. 4,787,325 to Black et al., which is owned by the assignee of the present invention. This approach involves use of a tiltable stacking surface to compensate for uneven height of the ends of the stack.
Another approach is described in the above U.S. Pat. No. 3,898,941 to Crawford et al., which employs a revolvable stack cartridge which rotates to compensate for build-up of a hem in a hemmed fabric piece such as a pocket. The fabric piece is delivered to the stacker cartridge by a stacker endless belt, and an elevator with spaced-apart lands which lifts the piece off the endless belt and "stuffs" the piece upwardly into a cartridge bottom opening. One drawback to this approach is that while the cartridge rotates to distribute the plies around the stack, the delivery method relies upon the resilience of the fabric piece to reassume or "remember" its flatness when the elevator withdraws so that the fabric piece will be retained within the cartridge. For thin pieces of material such as pinpoint oxford cloth cotton shirt material, this delivery method is rough on the material, is not reliable, and sometimes results in creases in the pocket. Moreover, the stacker shown in this patent is limited in the size range of plies it can handle, because of the fixed opening size in the cartridge bottom.